1. Field of the Invention
The present invention relates to a head gimbal assembly with a light guide structure and an information recording/reproducing apparatus which record or reproduce various kinds of pieces of information in or from magnetic recording media by utilizing spotlight that is condensed light.
2. Background Information
In recent years, along with an increase in the storage capacity of a hard disk or the like included in computer equipment, the information recording density for a single recording surface has increased. For example, in order to increase the recording capacity per unit area on a magnetic disk, the surface recording density has to be raised. However, as the recording density gets higher, a recording area on the recording medium occupied by one bit gets smaller. When the bit size decreases, energy representing information of one bit approaches to thermal energy at room temperature. Eventually, the recorded information may be reversed or deleted due to heat fluctuation, or any other problem relating to thermal demagnetization arises.
In a generally adopted longitudinal recording method that is a method of recording magnetic variations so that a magnetizing direction will be a longitudinal direction of a recording medium, disappearance of recorded information is liable to occur due to the foregoing thermal demagnetization. For overcoming this drawback, there is a tendency toward a perpendicular recording method of recording a magnetization signal in a direction perpendicular to the recording medium. The perpendicular recording method is a method of recording magnetic information according to the principle of approaching a sole magnetic pole to the recording medium. According to the method, a recording magnetic field is oriented in a direction nearly perpendicular to a recording film.
Information recorded with a perpendicular magnetic field is likely to remain stable in terms of energy, because the north pole and south pole hardly produce a loop in the surface of the recording film. Therefore, compared with the longitudinal recording method, the perpendicular recording method is unsusceptible to thermal demagnetization.
However, in recent years, recording media have been requested to support higher-density recording so as to meet a need for recording or reproducing a larger amount of higher-density information. Therefore, a medium whose coercive force is strong is beginning to be adopted as a recording medium in order to minimize an effect of a magnetic domain on an adjoining one or thermal fluctuation. Therefore, even when the aforesaid perpendicular recording method is adopted, it has become hard to record information in the recording medium.
In order to overcome the foregoing drawback, a hybrid magnetic recording method of locally heating a magnetic domain by utilizing spotlight that is condensed light, or near-field light that is condensed light, thus temporarily lowering a coercive force, and performing writing has been proposed. In particular, when near-field light is utilized, optical information in a region equal to or smaller than a wavelength of light regarded as a limit for existing optical systems can be dealt with. Therefore, record bits can be formed at a higher density than they can in existing optical information recording/reproducing apparatuses.
The configuration of a recording/reproducing apparatus utilizing near-field light is substantially identical to that of a magnetic disk drive. However, a near-field light utilization head is substituted for a magnetic head. The near-field light utilization head has a near-field light generation element formed with an optically microscopic aperture or a projection whose size is on the order of nanometers. The near-field light generation element is mounted in a slider realized using an air-cushion technology. The slider is attached to the distal end of a suspension, and floated at a constant height relative to a recording medium owing to a dynamic pressure. Eventually, the near-field light generation element accesses an arbitrary data mark existent in a recording medium. The near-field light utilization head is provided with a flexing capability to stabilize the posture thereof against a surge of a recording medium so that the slider will follow the recording medium rotated at a high speed. For the near-field light utilization head having the construction, a light introduction unit formed with an optical waveguide or the like is necessary to feed of light to the head. The optical waveguide includes an optical fiber. How efficiently light is introduced into the near-field light generation element and recording medium using the optical waveguide which offers lower freedom in layout than an electrical wiring does is a critical point of the recording/reproducing technology that utilizes near-field light.
For the near-field light utilization head, a technique of coupling the optical waveguide to the slider, and routing a microscopic beam spot to the near-field light generation element using a light reflecting surface, which reflects light that is propagated in a direction horizontal to a medium surface through the optical waveguide, so as to square the direction of propagation with the direction of an aperture has been discussed (refer to, for example, Patent Documents 1 and 2).
FIG. 13 schematically shows an information recording/reproducing apparatus employing a near-field light utilization head assembly (head gimbal assembly) 100. The near-field light utilization head assembly 100 includes an optical fiber 103, a suspension arm 104, a flexure 105, a slider 106, and a near-field light generation element (not shown). The flexure 105 is formed at the distal end of the suspension arm 104 so that the slider 106 will float while being disposed at a certain position relative to the recording medium 107. At this time, a recording medium 107 is rotated at a high-speed with the slider 106, in which the near-field light generation element is mounted, approached to the surface of the recording medium 107 at a distance ranging from several nanometers to several tens of nanometers.
The suspension arm 104 is fixed to a voice coil motor (not shown) through a fixing hole 104a, and can be moved in a radial direction of the recording medium 107 by the voice coil motor. Herein, the slider 106 has the near-field light generation element disposed therein so that the near-field light generation element will be opposed to the recording medium 107. Alight propagation unit that introduces a light beam emanating from a laser 101 into the slider 106 includes a lens 102 and the optical fiber 103 fixed to the suspension arm 104. If necessary, the light emanating from the laser 101 may be subjected to intensity modulation or the like by a circuit system 108.
In the foregoing near-field light utilization head assembly, when a force that presses the slider 106 toward the recording medium 107 and is imposed by the suspension arm 104 via the flexure 105, and a force that floats the slider 106 due to a wind pressure derived from the rotation of the recording medium 107 are balanced with each other, the slider 106 floats stably with a space, which ranges from several nanometers to several tens of nanometers, preserved relative to the recording medium 107. The suspension arm 104 is warped in advance toward the slider 106. With the spring force, a pressing force to be imposed on the slider 106 is generated. When the recording/reproducing apparatus operates, the warp of the suspension arm 104 is alleviated with a reactive force to the pressing force imposed on the slider 106.